Development and Characterization of a Porcine Liver Scaffold

The growing number of patients requiring liver transplantation for chronic liver disease cannot be currently met due to a shortage in donor tissue. As such, alternative tissue engineering approaches combining the use of acellular biological scaffolds and different cell populations (hepatic or progenitor) are being explored to augment the demand for functional organs. Our goal was to produce a clinically relevant sized scaffold from a sustainable source within 24 h, while preserving the extracellular matrix (ECM) to facilitate cell repopulation at a later stage. Whole porcine livers underwent perfusion decellularization via the hepatic artery and hepatic portal vein using a combination of saponin, sodium deoxycholate, and deionized water washes resulting in an acellular scaffold with an intact vasculature and preserved ECM. Molecular and immunohistochemical analysis (collagen I and IV and laminin) showed complete removal of any DNA material, together with excellent retention of glycosaminoglycans and collagen. Fourier-transform infrared spectroscopy (FTIR) analysis showed both absence of nuclear material and removal of any detergent residue, which was successfully achieved after additional ethanol gradient washes. Samples of the decellularized scaffold were assessed for cytotoxicity by seeding with porcine adipose-derived mesenchymal stem cells in vitro, these cells over a 10-day period showed attachment and proliferation. Perfusion of the vascular tree with contrast media followed by computed tomography (CT) imaging showed an intact vascular network. In vivo implantation of whole intact nonseeded livers, into a porcine model (as auxiliary graft) showed uniform perfusion macroscopically and histologically. Using this method, it is possible to create an acellular, clinically sized, liver scaffold with intact vasculature in less than 24 h.

Development of a novel hybrid bioactive hydrogel for future clinical applications

Three-dimensional hydrogels are ideal for tissue engineering applications due to their structural integrity and similarity to native soft tissues; however, they can lack mechanical stability. Our objective was to develop a bioactive and mechanically stable hydrogel for clinical application. Auricular cartilage was decellularised using a combination of hypertonic and hypotonic solutions with and without enzymes to produce acellular tissue. Methacryloyl groups were crosslinked with alginate and PVA main chains via 2-aminoethylmathacrylate and the entire macromonomer further crosslinked with the acellular tissue. The resultant hydrogels were characterised for its physicochemical properties (using NMR), in vitro degradation (via GPC analysis), mechanical stability (compression tests) and in vitro biocompatibility (co-culture with bone marrow-derived mesenchymal stem cells). Following decellularisation, the cartilage tissue showed to be acellular at a significant level (DNA content 25.33 ng/mg vs. 351.46 ng/mg control tissue), with good structural and molecular integrity of the retained extra cellular matrix (s-GAG= 0.19 μg/mg vs. 0.65 μg/mg ±0.001 control tissue). Proteomic analysis showed that collagen subtypes and proteoglycans were retained, and SEM and TEM showed preserved matrix ultra-structure. The hybrid hydrogel was successfully cross-linked with biological and polymer components, and it was stable for 30 days in simulated body fluid (poly dispersal index for alginate with tissue was stable at 1.08 and for PVA with tissue was stable at 1.16). It was also mechanically stable (Young's modulus of 0.46 ± 0.31 KPa) and biocompatible, as it was able to support the development of a multi-cellular feature with active cellular proliferation in vitro. We have shown that it is possible to successfully combine biological tissue with both a synthetic and natural polymer and create a hybrid bioactive hydrogel for clinical application.

Tracheal Replacement Therapy with a Stem Cell-Seeded Graft: Lessons from Compassionate Use Application of a GMP-Compliant Tissue-Engineered Medicine

Tracheal replacement for the treatment of end‐stage airway disease remains an elusive goal. The use of tissue‐engineered tracheae in compassionate use cases suggests that such an approach is a viable option. Here, a stem cell‐seeded, decellularized tissue‐engineered tracheal graft was used on a compassionate basis for a girl with critical tracheal stenosis after conventional reconstructive techniques failed. The graft represents the first cell‐seeded tracheal graft manufactured to full good manufacturing practice (GMP) standards. We report important preclinical and clinical data from the case, which ended in the death of the recipient. Early results were encouraging, but an acute event, hypothesized to be an intrathoracic bleed, caused sudden airway obstruction 3 weeks post‐transplantation, resulting in her death. We detail the clinical events and identify areas of priority to improve future grafts. In particular, we advocate the use of stents during the first few months post‐implantation. The negative outcome of this case highlights the inherent difficulties in clinical translation where preclinical in vivo models cannot replicate complex clinical scenarios that are encountered. The practical difficulties in delivering GMP grafts underscore the need to refine protocols for phase I clinical trials. Stem Cells Translational Medicine2017;6:1458–1464

Creation of an Acellular Vaginal Matrix for Potential Vaginal Augmentation and Cloacal Repair

STUDY OBJECTIVE

Our aim was to use porcine vagina to create a vaginal matrix and test its cellular biocompatibility.

DESIGN, SETTING, AND PARTICIPANTS

Vagina was harvested from pigs and decellularized (DC) using a combination of detergents (Triton X-100 and sodium deoxycholate) and enzymes (DNAse/RNAse).

INTERVENTIONS

The presence of cellular material, collagen structural integrity, and basement membrane proteins were assessed histologically. To address cytocompatibility, porcine adipose-derived mesenchymal stem cells were harvested from abdominal fat together with vaginal epithelial cells and seeded onto the mucosal aspect of the vaginal scaffold. Both cell populations were seeded individually and assessed histologically at days 3 and 10.

MAIN OUTCOME MEASURES AND RESULTS

The combination of enzymes and detergents resulted in a totally acellular matrix with very low DNA amount (control = 97.5 ng/μL ± 10.8 vs DC = 40.1 ng/μL ± 0.33; P = .02). The extracellular matrix showed retention of collagen fibers and elastin and a 50% retention in glycosaminoglycan content (control = 1.18 μg/mg ± 0.28; DC = 1.35 μg/mg ± 0.1; P = .03) and an intact basement membrane (positive for laminin and collagen IV). Seeded scaffolds showed cell attachment with adipose-derived mesenchymal stem cells and vaginal epithelial cells at days 3 and 10.

CONCLUSION

It is possible to generate an acellular porcine vaginal matrix capable of supporting cells to reconstruct the vagina for future preclinical testing, and holds promise for creating clinically relevant-sized tissue for human application.

Annexin A12-26 Treatment Improves Skin Heterologous Transplantation by Modulating Inflammation and Angiogenesis Processes

Skin graft successful depends on reduction of local inflammation evoked by the surgical lesion and efficient neovascularization to nutrition the graft. It has been shown that N-terminal portion of the Annexin A1 protein (AnxA1) with its anti-inflammatory properties induces epithelial mucosa repair and presents potential therapeutic approaches. The role of AnxA1 on wound healing has not been explored and we investigated in this study the effect of the peptide Ac2-26 (N-terminal AnxA1 peptide Ac2-26; AnxA1_2-26) on heterologous skin scaffolds transplantation in BALB/c mice, focusing on inflammation and angiogenesis. Treatment with AnxA1_2-26, once a day, from day 3-60 after scaffold implantation improved the take of the implant, induced vessels formation, enhanced gene and protein levels of the vascular growth factor-A (VEGF-A) and fibroblast influx into allograft tissue. It also decreased pro- while increasing anti-inflammatory cytokines. The pro-angiogenic activity of AnxA1_2-26 was corroborated by topical application of AnxA1_2-26 on the subcutaneous tissue of mice. Moreover, treatment of human umbilical endothelial cells (HUVECs) with AnxA1_2-26 improved proliferation, shortened cycle, increased migration and actin polymerization similarly to those evoked by VEGF-A. The peptide treatment instead only potentiated the tube formation induced by VEGF-A. Collectively, our data showed that AnxA1_2-26 treatment favors the tissue regeneration after skin grafting by avoiding exacerbated inflammation and improving the angiogenesis process.

Regeneration of the oesophageal muscle layer from oesophagus acellular matrix scaffold using adipose-derived stem cells

This study explored the feasibility of constructing a tissue engineered muscle layer in the oesophagus using oesophageal acellular matrix (OAM) scaffolds and human aortic smooth muscle cells (hASMCs) or human adipose-derived stem cells (hASCs). The second objective was to investigate the effect of hypoxic preconditioning of seeding cells on cell viability and migration depth. Our results demonstrated that hASMCs and hASCs could attach and adhere to the decellularized OAM scaffold and survive and proliferate for at least 7 days depending on the growth conditions. This indicates adipose-derived stem cells (ASCs) have the potential to substitute for smooth muscle cells (SMCs) in the construction of tissue engineered oesophageal muscle layers.

In vivo implantation of a tissue engineered stem cell seeded hemi-laryngeal replacement maintains airway, phonation, and swallowing in pigs

Laryngeal functional impairment relating to swallowing, vocalisation, and respiration can be life changing and devastating for patients. A tissue engineering approach to regenerating vocal folds would represent a significant advantage over current clinical practice. Porcine hemi-larynx were de-cellularised under negative pressure. The resultant acellular scaffold was seeded with human bone marrow derived mesenchymal stem cells and primary human epithelial cells. Seeded scaffolds were implanted orthotopically into a defect created in the thyroid cartilage in 8 pigs and monitored in vivo for 2 months. In vivo assessments consisted of mucosal brushing and bronchoscopy at 1, 2, 4, and 8 weeks post implantation followed by histological evaluation post termination. The implanted graft had no adverse effect on respiratory function in 6 of the 8 pigs; none of the pigs had problems with swallowing or vocalisation. Six out of the 8 animals survived to the planned termination date; 2 animals were terminated due to mild stenosis and deep tissue abscess formation, respectively. Human epithelial cells from mucosal brushings could only be identified at Weeks 1 and 4. The explanted tissue showed complete epithelialisation of the mucosal surface and the development of rudimentary vocal folds. However, there was no evidence of cartilage remodelling at the relatively early censor point. Single stage partial laryngeal replacement is a safe surgical procedure. Replacement with a tissue engineered laryngeal graft as a single procedure is surgically feasible and results in appropriate mucosal coverage and rudimentary vocal fold development.

A comparison of tracheal scaffold strategies for pediatric transplantation in a rabbit model

OBJECTIVES/HYPOTHESIS

Despite surgical advances, childhood tracheal stenosis is associated with high morbidity and mortality. Various tracheal scaffold strategies have been developed as the basis for bioengineered substitutes, but there is no consensus on which may be superior in vivo. We hypothesized that there would be no difference in morbidity and mortality between three competing scaffold strategies in rabbits.

STUDY DESIGN

Pilot preclinical study.

METHODS

Tracheal scaffolds were prepared by three methods that have been applied clinically and reported: preserved cadaveric ("Herberhold") allografts, detergent-enzymatically decellularized allografts, and synthetic scaffolds (nanocomposite polymer [polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU)]). Scaffolds were implanted into cervical trachea of New Zealand White rabbits (n = 4 per group) without cell seeding. Control animals (n = 4) received autotransplanted tracheal segments using the same technique. Animals underwent bronchoscopic monitoring of the grafts for 30 days. Macroscopic evaluation of tissue integration, graft stenosis, and collapsibility and histological examinations were performed on explants at termination.

RESULTS

All surgical controls survived to termination without airway compromise. Mild to moderate anastomotic stenosis from granulation tissue was detected, but there was evidence suggestive of vascular reconnection with minimal fibrous encapsulation. In contrast, three of the four animals in the Herberhold and POSS-PCU groups, and all animals receiving decellularized allografts, required early termination due to respiratory distress. Herberhold grafts showed intense inflammatory reactions, anastomotic stenoses, and mucus plugging. Synthetic graft integration and vascularization were poor, whereas decellularized grafts demonstrated malacia and collapse but had features suggestive of vascular connection or revascularization.

CONCLUSIONS

There are mirror-image benefits and drawbacks to nonrecellularized, decellularized, and synthetic grafts, such that none emerged as the preferred option. Results from prevascularized and/or cell-seeded grafts (as applied clinically) may elucidate clearer advantages of one scaffold type over another.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E449-E457, 2017.

Tracheal Replacement Therapy with a Stem Cell-Seeded Graft: Lessons from Compassionate Use Application of a GMP-Compliant Tissue-Engineered Medicine

Tracheal replacement for the treatment of end-stage airway disease remains an elusive goal. The use of tissue-engineered tracheae in compassionate use cases suggests that such an approach is a viable option. Here, a stem cell-seeded, decellularized tissue-engineered tracheal graft was used on a compassionate basis for a girl with critical tracheal stenosis after conventional reconstructive techniques failed. The graft represents the first cell-seeded tracheal graft manufactured to full good manufacturing practice (GMP) standards. We report important preclinical and clinical data from the case, which ended in the death of the recipient. Early results were encouraging, but an acute event, hypothesized to be an intrathoracic bleed, caused sudden airway obstruction 3 weeks post-transplantation, resulting in her death. We detail the clinical events and identify areas of priority to improve future grafts. In particular, we advocate the use of stents during the first few months post-implantation. The negative outcome of this case highlights the inherent difficulties in clinical translation where preclinical in vivo models cannot replicate complex clinical scenarios that are encountered. The practical difficulties in delivering GMP grafts underscore the need to refine protocols for phase I clinical trials. Stem Cells Translational Medicine 2017;6:1458-1464.

Mechanisms underlying heterologous skin scaffold-mediated tissue remodeling

Biocompatibility of two newly developed porcine skin scaffolds was assessed after 3, 14, 21 and 90 days of implantation in rats. Both scaffolds showed absence of cells, preservation of ECM and mechanical properties comparable to non-decellularised skin before implantation. Host cell infiltration was much prominent on both scaffolds when compared to Permacol (surgical control). At day 3, the grafts were surrounded by polymorphonuclear cells, which were replaced by a notable number of IL-6-positive cells at day 14. Simultaneously, the number of pro-inflammatory M1-macrophage was enhanced. Interestingly, a predominant pro-remodeling M2 response, with newly formed vessels, myofibroblasts activation and a shift on the type of collagen expression was sequentially delayed (around 21 days). The gene expression of some trophic factors involved in tissue remodeling was congruent with the cellular events. Our findings suggested that the responsiveness of macrophages after non-crosslinked skin scaffolds implantation seemed to intimately affect various cell responses and molecular events; and this range of mutually reinforcing actions was predictive of a positive tissue remodeling that was essential for the long-standing success of the implants. Furthermore, our study indicates that non-crosslinked biologic scaffold implantation is biocompatible to the host tissue and somehow underlying molecular events involved in tissue repair.

Stem Cell-Based Tissue-Engineered Laryngeal Replacement

Patients with laryngeal disorders may have severe morbidity relating to swallowing, vocalization, and respiratory function, for which conventional therapies are suboptimal. A tissue‐engineered approach would aim to restore the vocal folds and maintain respiratory function while limiting the extent of scarring in the regenerated tissue. Under Good Laboratory Practice conditions, we decellularized porcine larynges, using detergents and enzymes under negative pressure to produce an acellular scaffold comprising cartilage, muscle, and mucosa. To assess safety and functionality before clinical trials, a decellularized hemilarynx seeded with human bone marrow‐derived mesenchymal stem cells and a tissue‐engineered oral mucosal sheet was implanted orthotopically into six pigs. The seeded grafts were left in situ for 6 months and assessed using computed tomography imaging, bronchoscopy, and mucosal brushings, together with vocal recording and histological analysis on explantation. The graft caused no adverse respiratory function, nor did it impact swallowing or vocalization. Rudimentary vocal folds covered by contiguous epithelium were easily identifiable. In conclusion, the proposed tissue‐engineered approach represents a viable alternative treatment for laryngeal defects. Stem Cells Translational Medicine2017;6:677–687

Characterization of a biologically derived rabbit tracheal scaffold

There is a clinical need to provide replacement tracheal tissue for the pediatric population affected by congenital defects, as current surgical solutions are not universally applicable. A potential solution is to use tissue engineered scaffold as the framework for regenerating autologous tissue. Rabbit trachea were used and different detergents (Triton x-100 and sodium deoxycholate) and enzymes (DNAse/RNAse) investigated to create a decellularization protocol. Each reagent was initially tested individually and the outcome used to design a combined protocol. At each stage the resultant scaffold was assessed histologically, molecularly for acellularity and matrix preservation. Immunogenicity of the final scaffold was assessed by implantation into a rat model for 4 weeks. Both enzymes and detergents were required to produce a completely acellular (DNA content 42.78 ng/mg) scaffold with preserved collagen and elastin however, GAG content were reduced (8.78 ± 1.35 vs. 5.5 ± 4.8). Following in vivo implantation the scaffold elicited minimal immune response and showed significant cellular infiltration and vasculogenesis. The luminal aspect of the implanted scaffold showed infiltration of host derived cells, which were positive for pan cytokeratin. It is possible to create biologically derived biocompatible scaffolds to address specific pediatric clinical problems. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2126-2135, 2017.

Characterisation of porcine dermis scaffolds decellularised using a novel non-enzymatic method for biomedical applications

Off-the-shelf availability of tissue-engineered skin constructs, tailored by different combinations of reagents to produce a highly preserved biological matrix is often the only means to help patients suffering skin damage. This study assessed the effect of five different decellularisation methods on porcine dermal scaffolds with regard to matrix composition, biomechanical strength, and cytotoxicity using an in vitro biocompatibility assay. Results demonstrated that four out of the five tested decellularisation protocols were efficient in producing acellular scaffolds. Nevertheless, decellularisation method using osmotic shock without enzymatic digestion showed to be efficient not only in removing cellular material and debris from dermal scaffolds but was also beneficial in the preservation of extracellular matrix components (glycosaminoglycans and collagen). Histological assessment revealed that the dermal architecture of coarse collagen bundles was preserved. Examinations by scanning electron microscopy and transmission electron microscopy showed that the arrangement and ultrastructure of collagen fibrils in the scaffolds were retained following non-enzymatic method of decellularisation and also after collagen crosslinking using genipin. Moreover, this decellularised scaffold was not only shown to be biologically compatible when co-cultured with bone marrow-derived mesenchymal stem cells and fibroblasts, but also stimulated the cells to release trophic factors essential for tissue regeneration.

Pilot study of a novel vacuum-assisted method for decellularization of tracheae for clinical tissue engineering applications

Tissue engineered tracheae have been successfully implanted to treat a small number of patients on compassionate grounds. The treatment has not become mainstream due to the time taken to produce the scaffold and the resultant financial costs. We have developed a method for decellularization (DC) based on vacuum technology, which when combined with an enzyme/detergent protocol significantly reduces the time required to create clinically suitable scaffolds. We have applied this technology to prepare porcine tracheal scaffolds and compared the results to scaffolds produced under normal atmospheric pressures. The principal outcome measures were the reduction in time (9 days to prepare the scaffold) followed by a reduction in residual DNA levels (DC no-vac: 137.8±48.82 ng/mg vs. DC vac 36.83±18.45 ng/mg, p<0.05.). Our approach did not impact on the collagen or glycosaminoglycan content or on the biomechanical properties of the scaffolds. We applied the vacuum technology to human tracheae, which, when implanted in vivo showed no significant adverse immunological response. The addition of a vacuum to a conventional decellularization protocol significantly reduces production time, whilst providing a suitable scaffold. This increases clinical utility and lowers production costs. To our knowledge this is the first time that vacuum assisted decellularization has been explored. Copyright © 2015 John Wiley & Sons, Ltd.

Ultrasound-guided spinal anaesthesia in obstetrics: is there an advantage over the landmark technique in patients with easily palpable spines?

BACKGROUND

Data are scarce on the advantage of ultrasound-guided spinal anaesthesia in patients with easily identifiable bony landmarks. In this study, we compared the use of ultrasound to the landmark method in patients with no anticipated technical difficulty, presenting for caesarean delivery under spinal anaesthesia.

METHODS

A total of 150 pregnant women were recruited in this randomized, controlled study. Ultrasound examination and spinal anaesthesia were performed by three anaesthetists with experience in ultrasound-guided neuraxial block. Patients were randomized to either the Ultrasound Group (n=75) or the Landmark Group (n=75). In both groups the level of L3-4 or L4-5 was identified by ultrasound (transverse and longitudinal approach) or palpation. The primary outcome was the procedure time, measured from the time of skin puncture by the introducer to the time of viewing cerebrospinal fluid at the hub of the spinal needle. Secondary outcomes were the number of skin punctures, number of passes, and incidence of successful spinal blockade.

RESULTS

The average procedure time, number of skin punctures and needle passes, were similar in both groups. The number of patients with successful spinal anaesthesia after one puncture was not statistically different between the groups.

CONCLUSION

The present results indicate that when performed by anaesthetists experienced in both ultrasound and landmark techniques, the use of ultrasound does not appear to increase the success rate of spinal anaesthesia, or reduce the procedure time or number of attempts in obstetric patients with easily palpable spines.

Biocompatibility and potential of decellularized porcine small intestine to support cellular attachment and growth

The aim of this study was to decellularize a 30 cm long segment of porcine small intestine, determine its in vivo behaviour and assess the type of immunological reaction it induces in a quantitative manner. A segment of porcine ileum up to 30 cm long, together with its attached vasculature, was decellularized via its mesenteric arcade as a single entity. The quality of the acellular scaffold was assessed histologically and using molecular tools. The host response to the scaffold was evaluated in a rodent model. Stereological techniques were incorporated into quantitative analysis of the phenotype of the macrophages infiltrating the scaffold in vivo. Lengths of ileal scaffold, together with its attached vasculature, were successfully decellularized, with no evidence of intact cells and DNA or collagen and GAGs overdegradation. Analysis of explants harvested over 2 months postimplantation revealed full-thickness recellularization and no signs of foreign body or immune reactions. Macrophage profiling proved that between weeks 4 and 8 in vivo there was a switch from an M1 (pro-inflammatory) to an M2 (pro-remodelling) type of response. We show here that the decellularization process results in a biocompatible and non-toxic matrix that upon implantation triggers cellular infiltration and angiogenesis, primarily characterized by a pro-remodelling type of mononuclear response, without inducing foreign body reaction or fibrosis.

The development and implantation of a biologically derived allograft scaffold

Biologically derived scaffolds are becoming viable treatment options for tissue/organ repair and regeneration. A continuing hurdle is the need for a functional blood supply to and from the implanted scaffold. We have addressed this problem by constructing an acellular ileal scaffold with an attached vascular network suitable for implantation and immediate reperfusion with the host's blood. Using a vascular perfusion approach, a segment of porcine ileum up to 30 cm long, together with its attached vasculature, was decellularized as a single entity. The quality of the decellularized scaffold was assessed histologically and using molecular tools. To establish vascular perfusion potentials of the scaffold, a right-sided nephrectomy and end-to-end anastomosis of the decellularized scaffold's vasculature to a renal artery and vein were performed in a pig of similar size to the donor animal. Lengths of ileal scaffold, together with its attached vasculature, were successfully decellularized, with no evidence of intact cells/nuclear material or collagen degradation. The scaffold's decellularized vascular network demonstrated optimum perfusion at 1, 2 and 24 h post-implantation and the mesenteric arcade remained patent throughout the assessment. The 1, 2 and 24 h explanted scaffolds demonstrated signs of cellular attachment, with cells positive for CD68 and CD133 on the vascular luminal aspect. It is possible to decellularize clinically relevant lengths of small intestine, together with the associated vasculature, as a single segment. The functional vascular network may represent a route for recellularization for future regeneration of bowel tissue for patients with short bowel syndrome.

Esophageal tissue engineering: A new approach for esophageal replacement

A number of congenital and acquired disorders require esophageal tissue replacement. Various surgical techniques, such as gastric and colonic interposition, are standards of treatment, but frequently complicated by stenosis and other problems. Regenerative medicine approaches facilitate the use of biological constructs to replace or regenerate normal tissue function. We review the literature of esophageal tissue engineering, discuss its implications, compare the methodologies that have been employed and suggest possible directions for the future. Medline, Embase, the Cochrane Library, National Research Register and ClinicalTrials.gov databases were searched with the following search terms: stem cell and esophagus, esophageal replacement, esophageal tissue engineering, esophageal substitution. Reference lists of papers identified were also examined and experts in this field contacted for further information. All full-text articles in English of all potentially relevant abstracts were reviewed. Tissue engineering has involved acellular scaffolds that were either transplanted with the aim of being repopulated by host cells or seeded prior to transplantation. When acellular scaffolds were used to replace patch and short tubular defects they allowed epithelial and partial muscular migration whereas when employed for long tubular defects the results were poor leading to an increased rate of stenosis and mortality. Stenting has been shown as an effective means to reduce stenotic changes and promote cell migration, whilst omental wrapping to induce vascularization of the construct has an uncertain benefit. Decellularized matrices have been recently suggested as the optimal choice for scaffolds, but smart polymers that will incorporate signalling to promote cell-scaffold interaction may provide a more reproducible and available solution. Results in animal models that have used seeded scaffolds strongly sug- gest that seeding of both muscle and epithelial cells on scaffolds prior to implantation is a prerequisite for complete esophageal replacement. Novel approaches need to be designed to allow for peristalsis and vascularization in the engineered esophagus. Although esophageal tissue engineering potentially offers a real alternative to conventional treatments for severe esophageal disease, important barriers remain that need to be addressed.

Altered placental development in pregnancies resulting in sudden infant death syndrome (SIDS)

BACKGROUND

Sudden infant death syndrome (SIDS) is postulated to be a developmental disorder originating during fetal life in utero. Knowledge regarding the intrauterine environment in which SIDS infants develop is, however, inadequate and how the placenta develops prior to a SIDS event has not been studied.

AIM

To investigate the morphological development of the placenta obtained from full-term infants who subsequently succumbed to SIDS.

STUDY DESIGN

To estimate the percentage and total volumes of the chorionic villi and villous trophoblast membrane using stereological techniques.

SUBJECTS

Placentas were obtained retrospectively from normal birthweight (SIDS-NBW n=18) and small-for-gestational age (SIDS-SGA, n=14) infants who had succumbed to SIDS, and compared to either control (n=8) or SGA placentas (n=7), respectively.

RESULTS

SIDS-NBW placentas displayed evidence of augmented villous growth shown by significantly greater volumes of placental chorionic villi (gas-exchanging (GE) villi) in comparison to controls; this was not observed for SIDS-SGA placentas. However, both SIDS-NBW and SIDS-SGA placentas displayed significantly greater volumes of the cytotrophoblast (CT) (SIDS-NBW only), syncytiotrophoblast (SIDS-SGA only) and syncytial knots (SCT-K) and those displaying apoptotic syncytial nuclei (AP SCT-K). In contrast, SGA placentas displayed significantly reduced volumes of chorionic villi, GE villi and the villous trophoblast indicating a SIDS-specific effect associated with augmented placental growth.

CONCLUSIONS

Our findings provide initial evidence that placental abnormality, although not necessarily causative, may precede a subset of SIDS cases supporting the hypothesis that the origins of SIDS begin during fetal life in utero.

Neocellularization and neovascularization of nanosized bioactive glass-coated decellularized trabecular bone scaffolds

In this study, the in vivo recellularization and neovascularization of nanosized bioactive glass (n-BG)-coated decellularized trabecular bone scaffolds were studied in a rat model and quantified using stereological analyses. Based on the highest amount of vascular endothelial growth factor (VEGF) secreted by human fibroblasts grown on n-BG coatings (0-1.245 mg/cm(2)), decellularized trabecular bone samples (porosity: 43-81%) were coated with n-BG particles. Grown on n-BG particles at a coating density of 0.263 mg/cm(2), human fibroblasts produced 4.3 times more VEGF than on uncoated controls. After 8 weeks of implantation in Sprague-Dawley rats, both uncoated and n-BG-coated samples were well infiltrated with newly formed tissue (47-48%) and blood vessels (3-4%). No significant differences were found in cellularization and vascularization between uncoated bone scaffolds and n-BG-coated scaffolds. This finding indicates that the decellularized bone itself may exhibit growth-promoting properties induced by the highly interconnected pore microarchitecture and/or proteins left behind on decellularized scaffolds. Even if we did not find proangiogenic effects in n-BG-coated bone scaffolds, a bioactive coating is considered to be beneficial to impart osteoinductive and osteoconductive properties to decellularized bone. n-BG-coated bone grafts have thus high clinical potential for the regeneration of complex tissue defects given their ability for recellularization and neovascularization.

Decellularized rabbit cricoarytenoid dorsalis muscle for laryngeal regeneration

OBJECTIVES

Although considerable progress has been made in regenerative medicine, a quantum step would be the replacement and/or regeneration of functional muscle tissue. For example, although patients' airways can now be successfully replaced with stem cell-based techniques, a much greater patient need would be addressed by regeneration of the muscles required for engineering a functional larynx, in which active movement is critical. The rabbit cricoarytenoid dorsalis muscle was chosen for the present study because it is equivalent to the posterior cricoarytenoid muscle, the only significant abductor muscle in human larynges.

METHODS

Rabbit cricoarytenoid dorsalis muscles were harvested, and different decellularization methods were compared by use of a combination of histologic, immunohistochemical, and molecular techniques. Decellularized scaffolds were implanted into Sprague-Dawley rats as part of a 2-week biocompatibility study to assess immunogenicity.

RESULTS

Decellularization with a combination of latrunculin B, potassium iodide, potassium chloride, and deoxyribonuclease resulted in total DNA clearance and reduced levels of major histocompatibility complex class II expression, with relative preservation of the scaffold's structural integrity (collagen, elastin, and glycosaminoglycan content). The scaffolds showed minimal signs of rejection at 2 weeks in a cross-species (xenotransplantation) study.

CONCLUSIONS

Decellularized laryngeal muscles, which are nonimmunogenic, may provide the optimal scaffold source for the generation of a fully functional tissue-engineered larynx.

Proteomic Analysis of Decellularized Tissue Engineered Laryngeal-Tracheal Scaffolds

Objective: The clinical success of a fully tissue-engineered tracheal transplant has indicated that there may be more to using decellularized tissue as a scaffold construct. It has been hypothesized that remnant polypeptides reside in these matrices. We sought to determine the proteome profile of a decellularized laryngeal-tracheal scaffold construct.

Method: A laryngeal-tracheal construct was fabricated using standard decellularization protocols and underwent immunohistochemistry, electron microscopy, biomechanical analysis, and qPCR for total DNA content. Samples from anatomical subsites were prepared for proteomic analysis. Tandem mass-spectrometry (LC-MS/MS) was used to identify peptide sequences and validated using multicolor immunohistochemistry and western blotting.

Results: Decellularization of laryngea-tracheal scaffold airway construct effectively removed cells, MHC components, and DNA while maintaining similar biomechanical properties to native (nondecellularized) tissue. We identified variable expression of polypeptides in the anatomical subsites of the airway scaffold construct. A minimum core set of polypeptides was identified with a subset of proteins with putative roles beyond structural integrity. Of particular interest were small molecular weight polypeptides known to have significant roles in epithelialization and angiogenesis.

Conclusion: We demonstrate that mass spectrometry can be used as a tool to accurately identify residual proteins in a laryngeal-tracheal scaffold. The identification of signaling proteins may be of crucial importance in designing the next generation of “intelligent” off-the-shelf scaffolds.

The relationship of various arch forms and cortical bone thickness

OBJECTIVE

Implants are being used in orthodontics as a reliable mode of anchorage. Among other factors, the cortical bone thickness plays a major role in determining the stability of these implants. The objective of this study was to study the relationship of various arch forms and the cortical bone thickness and to determine if the cortical bone thickness varies between various arch forms. This would help to determine the ideal length of an implant for a particular arch form.

MATERIALS AND METHODS

A cross sectional tomograph was obtained from 30 patients. Based on arch forms the patients' tomographs were equally divided into three basic square, tapered and ovoid categories, each consisting of 10 patients. Consequently, their buccal and lingual cortical plate thicknesses were measured.

RESULTS

The results showed that there was a statistically significant difference between the three arch forms, in which the square arch form had the greatest cortical bone thickness among the three arch forms.

CONCLUSION

Patients having a tapered arch form may require implants with greater length than patients having a square or an ovoid arch form. Since the availability of the cortical bone in square arch patients is greater, there is more stability for the implants in these cases; therefore, implants with a shorter length may be used in these cases.

Medical mortality in Pakistan: experience at a tertiary care hospital

AIM

To acquire systematic data on the causes of hospital mortality in Pakistan, a developing country with scant mortality records.

STUDY DESIGN

Retrospective review of death certificates and hospital charts of patients dying on general and specialty medical services at our hospital during one calendar year.

RESULTS

Of a total 10,590 admissions, 657 (6.2%) died in hospital. The deceased included 357 (54.4%) males and 299 (45.6%) females, with a collective median age of 63 years and mean length of stay 6.71 days (median 4 days, range 1-56 days). Primary cause of death was categorised as infectious (21.2%), pulmonary (17.2%), cancer related (15.7%), cardiovascular (12.6%), gastrointestinal and hepatic (10.8%), neurological (11.4%) and miscellaneous (11.1%). Within each category, the most common diagnoses were septicaemia (76.9% of infectious cases), pneumonia (55.7% of pulmonary cases), myocardial infarction (40.9% of cardiovascular), intracranial haemorrhage (37.3% of neurological), and cirrhosis (45.0% of gastrointestinal). There were multiple causes among malignant disorders with no single cause dominating. Patients with cardiovascular and pulmonary deaths tended to be older than the median age (p = 0.001), while patients with gastrointestinal and cancer related deaths tended to be younger than the median age (p = 0.001). Length of stay did not differ significantly among the various subgroups. About a quarter (26.4%) deaths occurred within 24 h of admission.

CONCLUSIONS

Infections, including septicaemia and pneumonia, are the leading causes of hospital mortality in our setting, followed by malignancy and cardiovascular causes. The overall mortality rate is comparable to published mortality data from other hospital settings.

Birth injuries in caesarian sections: cases of fracture femur and humerus following caesarian section

Long bone injuries are less common during caesarian section. Sometimes, they remain unnoticed to the operating surgeon but are frequently noted by attending physician or nurses. The aim of this case study is to remind the surgeon that any forceful extraction may result long bone injuries. So, care should be given during and after delivery to rule out injuries.

Effect of nanoparticulate bioactive glass particles on bioactivity and cytocompatibility of poly(3-hydroxybutyrate) composites

This work investigated the effect of adding nanoparticulate (29 nm) bioactive glass particles on the bioactivity, degradation and in vitro cytocompatibility of poly(3-hydroxybutyrate) (P(3HB)) composites/nano-sized bioactive glass (n-BG). Two different concentrations (10 and 20 wt %) of nanoscale bioactive glass particles of 45S5 Bioglass composition were used to prepare composite films. Several techniques (Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray) were used to monitor their surface and bioreactivity over a 45-day period of immersion in simulated body fluid (SBF). All results suggested the P(3HB)/n-BG composites to be highly bioactive, confirmed by the formation of hydroxyapatite on material surfaces upon immersion in SBF. The weight loss and water uptake were found to increase on increasing bioactive glass content. Cytocompatibility study (cell proliferation, cell attachment, alkaline phosphatase activity and osteocalcin production) using human MG-63 osteoblast-like cells in osteogenic and non-osteogenic medium showed that the composite substrates are suitable for cell attachment, proliferation and differentiation.

Pneumomediastinum, stomach wall and hepatic portal vein gas secondary to partial necrosis of the stomach wall

The combination of pneumomediastinum, gastric wall gas and hepatic portal vein gas is a challenging clinical problem. Although different causes of the individual gas sign have been reported in the literature, the cause of a triad of these signs in a single patient is less clear, and represents an extremely rare condition. A 65-year-old man presented with severe lower chest and epigastric pain of a few hours' duration. Initial assessment confirmed epigastric tenderness. Computed tomography showed pneumomediastinum, air in the stomach wall, hepatic portal vein gas and bowel dilatation. Small bowel and right colon dilatation was confirmed at laparotomy. The patient was treated subsequently with antibiotics to cover Gram-positive and Gram-negative bacteria, and anaerobes. The patient was discharged in good general condition on the 12th postoperative day. In conclusion, the triad of pneumomediastinum, gastric wall gas and hepatic portal vein gas is an extremely rare condition and associated with gastric necrosis.

IFPA meeting 2008 workshops report

Workshops are an important part of the IFPA annual meeting. At the IFPA meeting 2008 diverse topics were discussed in 12 themed workshops. Topics covered included: immunology of placentation; galectins and trophoblast invasion; signaling in implantation and invasion; markers to identify trophoblast subpopulations; placental pathology; placental toxicology; stereology; placental transport of fatty acids; placental mesenchymal stem cells; comparative placentation; trophoblast and neoplasia; trophoblast differentiation. This report is a summary of the various topics covered.

Prolonged Maintenance of Neointestine Using Subcutaneously Implanted Tubular Scaffolds in a Rat Model

Tissue-engineered small intestine offers a possible alternative to long-term parenteral nutrition or intestinal transplantation in patients with short bowel syndrome. The aim of this study was to investigate the prolonged development of neointestine grown on subcutaneously implanted scaffolds. Tubular polylactide-coglycolide (PLGA) scaffolds were implanted into adult Lewis rats. Four weeks after scaffold implantation, a suspension of organoid units was delivered to the lumen of each scaffold. Organoid units were manufactured from small intestine harvested from neonatal Lewis rats by partial digestion using collagenase and dispase. Scaffolds were removed at 4, 8, and 12 weeks after organoid unit implantation, processed to paraffin, and sectioned. Hematoxylin and eosin staining demonstrated well-developed and well-differentiated intestinal mucosa and a vascularised submucosa within the scaffolds at 4, 8, and 12 weeks. Appearances were similar to native small intestine. Immunohistochemistry performed using primary antibody against proliferating cell nuclear antigen, a marker for cellular proliferation, demonstrated positively staining cells within the mucosa and submucosa at all time points. In the mucosal layer these positively staining cells were found primarily in the crypts. These findings show that neointestinal mucosa can be maintained for at least 12 weeks on a subcutaneous PLGA scaffold, and the presence of actively proliferating cells at 12 weeks suggests potential for further development beyond this.

Pre-eclampsia and Fetal Growth Restriction: How Morphometrically Different is the Placenta?

Both pre-eclampsia (PET) and fetal growth restriction (FGR) pose a heavy burden on fetal and maternal health and may disrupt pregnancy outcome. Using design based stereological techniques, placental vascular and villous morphology were assessed to determine the individual role played by both PET and FGR on placental growth during the third trimester. The following placentas delivered between 25 and 41 weeks of gestation were included into the study; controls (n=16), PET (n=20), FGR (n=17) and PET-FGR (n=16). Each placenta was uniformly randomly sampled and the sampled tissue processed to paraffin. Sections were stained with a CD34 antibody and the following morphometric parameters estimated: volumes, surface areas, length, diameters and the shape factor of the villous (terminal and intermediate) and vascular placental features. For stereologically estimated parameters pure PET had an effect on IVS and terminal villi volume only. FGR alone or when coexisting with PET contributed towards significant reductions in volumetric and surface area terminal villous and vascular features. FGR factors also contributed towards a significant reduction in the lengths of all parameters estimated and in the terminal villi diameter. Additionally, FGR was associated with a significant difference in shape factor indices for both intermediate and terminal villi. This study has shown that PET on its own has limited influence on the placental morphology studied, since the vascular features estimated do not differ stereologically from age matched normal controls. However, placental morphology is different between PET and PET-FGR and between PET-FGR and FGR. PET and FGR may have a cumulative effect on placental villous and vascular morphology as seen in the PET-FGR but there is no synergistic effect. These morphological abnormalities may have major physiological implications in terms of placental function and fetal growth.

Maternal medicine: Morphometric placental villous and vascular abnormalities in early- and late-onset pre-eclampsia with and without fetal growth restriction

OBJECTIVE

To evaluate placental morphology in pregnancies complicated by early- and late-onset pre-eclampsia (PET) with and without fetal growth restriction (FGR) using stereological techniques.

DESIGN

A total of 69 pregnant women were studied. Twenty women had pregnancies complicated by PET, 17 by FGR and 16 by both PET and FUR; the remaining 16 were from gestational-age-matched controls. Each group was further classified into early onset (<34 weeks) and late onsets (>34 weeks) based on gestational ages.

SETTING

NPIMR at Northwick Park and St Marks Hospital.

POPULATION

placentae from pregnant women.

METHODS

Formalin-fixed, wax-embedded sections stained with anti-CD34 antibodies and counterstained with haematoxylin.

MAIN OUTCOME MEASURES

Volumes, surface areas, lengths, diameters and shape factors of the villous tissues and fetal vasculature in the intermediate and terminal villi of all the groups studied.

RESULTS

Terminal villi volume and surface area were compromised in early-onset PET cases, late-onset PET had no impact on peripheral villi or vasculature features. The morphology of the vascular and villous subcomponents in the intermediate and terminal villi was significantly influenced by late-onset FGR, whereas early-onset FGR caused a reduction in placental weight. Length estimates were not influenced by PET, FGR or age of onset. Intermediate arteriole shape factor was significantly reduced in late-onset FGR.

CONCLUSIONS

Isolated early-onset PET was associated with abnormal placental morphology, but placentas from late-onset PET were morphologically similar to placentas from gestational-age-matched controls, confirming the existence of two subsets of this condition and supporting the hypothesis that late-onset PET is a maternal disorder and not a placental disease.

Reviewing the use of carbon monoxide-releasing molecules (CO-RMs) in biology: implications in endotoxin-mediated vascular dysfunction

The inducible stress protein heme oxygenase-1 (HO-1) has been linked to tissue and organ protection against the deleterious actions of many pathological conditions, including endotoxin challenge. Similar protection can be achieved by the main products of heme oxygenase activity, namely bilirubin and carbon monoxide (CO). Since the identification of novel chemical compounds that liberate CO in biological systems (CO-releasing molecules or CO-RMs), our group and others have had access to a convenient and simple pharmacological tool that enables to study the role of CO in physiological functions. This article will review the scientific literature published to date on CO-RMs, with emphasis on the in vitro, ex vivo and in vivo experimental models employed to determine the contribution of CO to cellular mechanisms. In addition, we will report on the effect of heme oxygenase-related substances, such as bilirubin, CORM-3 and hemin, in a model of endotoxin-induced hypotension. Among the three different approaches examined, CORM-3 proved the most effective agent in reducing the fall in blood pressure caused by endotoxin. Furthermore, heme oxygenase-related substances affected the endotoxin-stimulated induction and distribution of hepatic HO-1 and inducible nitric oxide synthase (iNOS). Thus, it emerges that CO-RMs could exert important biological actions in the context of endotoxic-mediated dysfunction.

Pilot study: fibrin sealant in anal fistula model

PURPOSE

The aim of this study was to investigate the failure of fibrin sealant treatment for fistula-in-ano in an experimental porcine model and to determine histologic changes associated with the sealant and setons.

METHODS

Three surgically created fistulas were treated by seton drainage in each of eight male pigs. After 26 days, magnetic resonance imaging was performed and setons were removed. Two pigs were killed as controls for stereologic histologic fistula track assessment. In six, fistulas were curetted, and in four the fistulas were treated with fibrin sealant. In these four sealant and two seton pigs, magnetic resonance imaging was repeated a median of 47.5 days after fistula formation. The pigs were killed and stereologic histologic fistula track examination was performed to determine granulation tissue and fistula lumen volumes. These values were compared among control, seton, and sealant groups over time, and related to fistula volumes derived from magnetic resonance imaging.

RESULTS

Sealant was not visible microscopically within tracks, although some sections revealed a foreign body-type reaction. On stereologic assessment, granulation tissue volumes were smaller in sealant and seton groups than in controls (median, 88 vs. 187 vs. 453 mm3, respectively; P = 0.002) and decreased over time (median, 408 and 152 mm3 (Day 42) vs. 88 and 75 (Day 53), respectively; P = 0.002). Fistula lumen (P < 0.001), and granulation tissue combined with fistula lumen volumes (P = 0.002) were similarly smaller. Magnetic resonance imaging of fistula intensity was less in the sealant group than in the seton group and controls (mean, 777 vs. 978 vs. 1214 units/mm2, P = 0.003). Magnetic resonance imaging fistula volumes were least in sealant and seton groups vs. controls (P = 0.024), decreasing significantly in the sealant group over time (P = 0.018). No direct relationship was found between imaging and histologic volumes.

CONCLUSIONS

In an experimental porcine model of anal fistula, granulation tissue was still present, albeit diminished, following track curettage combined with seton or sealant therapy, and was minimal in the sealant group, confirming some benefit from this procedure. Eradication of all longstanding granulation tissue may ensure complete success of fibrin sealant therapy.

Experimental model of fistula-in-ano

PURPOSE

This study was designed to create and evaluate an experimental porcine model of fistula-in-ano.

METHODS

Initial cadaveric dissection enabled refinement of the technique for fistula formation and histoanatomical study of the porcine anal canal. Subsequently, three surgically created fistulas were treated by seton drainage in each of eight male pigs (weight, 38-41 kg). After 26 days, magnetic resonance imaging at 1.5 Tesla was performed and setons removed under general anesthesia, enabling clinical and microbiologic track assessment. Two pigs were killed for histologic fistula track assessment.

RESULTS

Histoanatomical assessment noted a rudimentary internal anal sphincter, together with structures resembling anal glands. Artificial fistulas persisted during seton drainage and were more often associated with fecal than skin-derived organisms compared with both perineal and anal canal swabs (P = 0.002). All six fistulas assessed histologically had a lumen, and abundant surrounding granulation tissue similar to that seen in human fistula-in-ano. Epithelialization was not evident in any track. Fistulas were visualized as high signal tracks using magnetic resonance imaging.

CONCLUSIONS

Porcine anal anatomy resembles that of humans, and an experimental model proved suitable when assessed by magnetic resonance imaging, microbiology, and histologically, which demonstrated abundant granulation tissue. This model could be further used to investigate fistula treatments.

Analyses of the potential oxygen transfer capability in placentae from infants succumbing to sudden infant death syndrome

BACKGROUND

Morphometric oxygen diffusive conductance (Dp) was estimated to assess the potential efficiency of oxygen transfer across the materno-fetal interface in placentae obtained from victims of sudden infant death syndrome (SIDS).

STUDY DESIGN

SIDS placentae were retrieved from archived storage and classified into normal birth weight (NBW, n=16), or small for gestational age (SGA, n=9) and compared against control placentae (n=40) or SGA (n=24) placentae. A combination of stereological techniques and physiological constants were used to estimate total Dp.

RESULTS

SIDS NBW cases showed a crucial reduction in fetal capillary surface area when compared with control placentae. SIDS SGA showed a number of deficiencies in basic volumetric and surface area parameters. Values for total and specific Dp in placentae in both SIDS groups were maintained at levels comparable with control and SGA cases, respectively.

CONCLUSION

Since more reductions were observed in SIDS SGA group, this suggests that factors responsible for these reductions maybe associated with SGA rather than being SIDS-specific factors.

Variation of CD8+ T-lymphocytes around the bronchial internal perimeter in chronic bronchitis

The variation of CD8+ cells has been determined around the internal perimeter of intrapulmonary bronchi in smokers with chronic bronchitis (CB), and the amount of tissue required to confidently estimate the true mean has been calculated. Lung specimens were obtained from 10 smokers with CB. Paraffin sections of intrapulmonary bronchi were immunostained and CD8+ cells counted in the epithelium and subepithelium in up to 10 sequential 1-mm segments around the internal perimeter of each airway. The percentage of counts falling between +/-20% of the final mean was 43.0% for epithelium and 40.9% for subepithelium. In 90% of subjects, the cumulative mean was stable after examination of subepithelial tissue associated with 5 mm of reticular basement membrane. There is considerable variation in the counts of CD8+ cells between adjacent 1-mm airway mucosal segments in chronic bronchitis. In order to achieve a representative count and to maximise statistical power to detect differences between study populations, subepithelial tissue including a minimum of 5 mm of reticular basement membrane length should be examined.

Elastase-induced changes in lung function: relationship to morphometry and effect of drugs

Intratracheal administration of porcine pancreatic elastase (PPE) produced a dose related decline in lung function, as assessed by changes in dynamic lung compliance (C(dyn)) in New Zealand White rabbits. This occurred within 24 h of administration and persisted for 56 days (n=6). These lung function changes were accompanied by histological evidence of emphysema in the lungs and were not mimicked by intratracheal administration of the proteolytic enzyme trypsin. Neither the lung function nor the histological changes induced by elastase could be prevented or reversed by either the glucocorticosteroid, dexamethasone, or all trans retinoic acid (ATRA).Our data suggest that local administration of elastase to the lungs of rabbits may provide a convenient way to assess the effects of drugs on the changes induced by elastase in airways.

Morphometric assessment of the oxygen diffusion conductance in placentae from pregnancies complicated by intra-uterine growth restriction

The morphometric oxygen diffusive conductance (D(p)) of the placenta provides a measure of the efficiency of oxygen transfer between the mother and the developing fetus. Any change in the D(p)may point towards possible adaptation in the light of altered oxygen transfer. Placentae from normal (n=40) and small for gestational age SGA (n=24) pregnancies were analysed using stereological techniques. Each placenta was uniform randomly sampled and tissue samples processed to wax infiltration and embedding using conventional histological preparatory methods. A combination of stereological techniques and physiological constants were used to estimate the partial conductances across the five major tissue compartments involved in oxygen transfer. There was a significant reduction in both fetal birthweight and placental weight in the SGA group when compared with controls. A decrease in both chorionic (S(cv)) and fetal capillary (S(fc)) surface area was also observed in SGA placentae when compared with controls (P>0.001). Villous membrane harmonic thickness (T(vm)) was reduced in the SGA placentae (2.33 microm) when compared with controls (2.67 microm P=0.019). This resulted in a reduction in the minimum D(p)in SGA placentae when compared with controls (P=0.023). Adjusting for fetal weight resulted in no difference in the specific diffusive conductance. Changes in T(vm)in SGA placentae combined with changes in basic surface areas were insufficient to maintain overall D(p)values comparable with control placentae.

Prevalence and associated impairments of mild mental retardation in six- to ten-year old children in Pakistan: a prospective study

The aim of this study was to find the prevalence of mild mental retardation (MMR) in 6-10-y-old children in a prospectively followed cohort in Pakistan from four areas with different socioeconomic conditions. Retarded children were identified by a two-step method, comprising a household screening with the Ten Questions Screening in 649 families followed by clinical investigation and psychometric testing (WISC-R and Griffiths) of the 132 children found by the screening. The overall prevalence of MMR among 6-10-y-old children was 6.2%. The distribution of MMR was uneven, with 1.2% among children from the upper-middle class, 4.8% in the village, 6.1% in the urban slum and 10.5% in the poor periurban slum area. Additional impairments were found in 75% of the children with MMR, of which speech impairment was the most common.

CONCLUSION

The prevalence of MMR was found to be higher in a developing country than in developed countries. It also seemed to be related to poor socioeconomic conditions, as the prevalence in the upper-middle class was comparable to figures from developed countries, while the prevalence in children from poor population groups was much higher.